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Capacitor Rebuilding for Fun or Profit 


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Capacitor Rebuilding for Fun or 


Written By: Don Fox 


I restore antique radios to make the cash I need to play with my toys. Audiophiles are happy, 
so is my wallet. 

Mainly we do this simply because the 'original' parts are no longer available, or if they are, 
the price is exorbitant. 

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Capacitor Rebuilding for Fun or Profit 

Step 1 — Capacitor Rebuilding for Fun or Profit 

• When working in an old TV, Audio 
Amplifier, or Turntable, invariably I 
will run across capacitors of all 
types, Paper, mica, electrolytic, 
etc.... Generally when we run into 
caps that are of the electrolytic 
type they are mostly dry, or drying 
out. Some common practices have 
people just shotgunning the 
problem by swapping out all old 
caps with new technology. 

• Electrically equivalent but to 

some of my audiophile buds, it is 
blasphemy bordering on the 
obscene. It should also be noted... 
with times being what they are... 
You can command a little bit more 
for the units you choose to sell 
noting no new tech parts are there. 

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Capacitor Rebuilding for Fun or Profit 

Step 2 

• Let's start off with the offending 
part. A dual cap 50uf@l50wvdc in 
a waxen pressed board container. 

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Capacitor Rebuilding for Fun or Profit 

Step 3 

• Nicely, notice I did not use the 
word gently... Smiley Take an old 
soldering iron and use it to liquefy 
the resin and waxen plug in the end 
of the cap. Some liquid will co- 
operate and gently flow out, the 
rest will become soft like putty, and 
easily manageable with the tip of a 
small flat screwdriver. NOW, 
gentle heating with a HAIR DRYER 
will loosen the material near the 
wall, and then clean it with the 
screwdriver. When you get to 
them, cut the cap leads at the 
rivets. (You will see them and feel 
them with the melting iron) 

• When you get deep enough, take 
soldering iron and press it into the 
center of the old cap material. This 
will make a pilot hole. 

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Capacitor Rebuilding for Fun or Profit 

Step 4 

• Take a 3/8th's drill and while 
holding the cap shell by the side, 
measure (with the drill bit) how 
deep you can go, less about 3/4" 
just for safety, and mark it with 
some tape . Now, take the cap and 
hold it with gloves or whatever you 
feel comfortable with... and gently 
drill into the cap materials. If you 
go slowly, the drill SHOULD take a 
grab onto the whole core when it 
gets into the upper resin and the 
whole core SHOULD spin in the 
cap barrel. STOP drilling when you 
get to the tape mark or the core 

Step 5 

• Now grab the core with a hooked 
dental pick, o-ring tool, or even a 
small bit of wire with a slight hook 
in it. Pull out your prize. 

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Capacitor Rebuilding for Fun or Profit 

Step 6 

• Here are your 5 constituent parts of 
the cap, less the plug material. 

Step 7 

• Now, here comes the fun part. 
Take the replacement value caps, 
for ME, alone, I used three 
25uf@250v caps per side of the 
cap. Remember, CAPS IN 
keeping the working voltages the 
same. Yes, I purposely chose 3 
caps because they will form a 
triangular pattern for better 
centering. I put a large loop on 
these negatives, since this will be 
the common point for the cap. 

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Capacitor Rebuilding for Fun or Profit 

Step 8 

• Cap bundle with the positives wired 
and the rest is now the pigtail for 
one of the positive leads. 

Step 9 

• Needed to be done twice. Leave 
enough wire on the second bundle 
to hook them together. 

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Capacitor Rebuilding for Fun or Profit 

Step 10 

• Take the negative lead from the 
second cap, and feed it through the 
center of the first cap, and cut it 
long enough to hook it to the first 
bundle's loop(remember that?) 

Step 11 

• Remove the second cap bundle. 
Take some black tape and put a 
layer or two on the top of the first 
bundle. Poke a hole in it with the tip 
of a soldering iron. 

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Capacitor Rebuilding for Fun or Profit 

Step 12 

• Reassemble the two cap bundles, 
soldering the negative lead from 
the second bundle, and the 
black(or whatever color it is) to the 
lug on the first bundle. Attach the 
remaining original wires to the 
positive leads. 

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Capacitor Rebuilding for Fun or Profit 

Step 13 

• Now, insert the whole new stack 'o 
caps into the old shell. Take a 
moment to admire your work. 

• (no pics of the next 2 steps) Cut 
out a small piece of gray cardboard 
. The annoying fiberboard most 
things are shipped in or used as 
card material. Cut it down to the 
size of the inside of the cap shell. 
Poke 3 small holes for the leads. 
Feed the leads through the holes 
and press the fiber circle into the 
cap body, pushing it in about 1/2". 

• Take your melting iron, and using a 
small candle(unlit) preferably white, 
but not a brilliant white, melt the 
bottom of the candle filling in the 
bottom of the cap body. This is 
simply for aesthetics, but what the 
heck. Don't be lazy and burn the 
candle to drip. There is conductive 
carbon in the dripped wax. 

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Capacitor Rebuilding for Fun or Profit 

Step 14 

• Tahdah! A brand new 'antique' cap. Take a second moment to chuckle. 

• Re-inserted into the radio/amplifier. Smile knowingly to yourself. 

This document was last generated on 2012-11-03 03:30:09 AM. 

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